we have been monitoring a 11kw water pump. It is mounted on a spring base and is controlled by a VSD. There are two identical pumps which alternate duty.
One of the Motors soon after changing the motor was operating significantly hotter than the other one. One operates at about 60 degree C and the other 90 degrees C. Mesuring the amps and they are within nameplate specs.
Both motors have class F insulation so they should handle this temp. But why diference between motors.
On inspection last week one of the motors was noted to have excessive noise in the Drive End bearing. Listening with Ultrasonics and it sounded like a bearing problem. Oil/grese was noted to have dripped out of the drive end bearing of the motor, and was evident on the concrete below. Added grease to bearings and it quietened down but was still evident.
Vibration readings from previous inspections and current readings were about the same.
Client deceided he wanted to change the bearings on the motor. Bearings were removed and were in good condition. Motor was surge tested and no faults were found in the windings.
On inspection of the bearing jounals on the motor shaft. The drive end Journal had very fine lines vertically around the journal. and very tiny dots ( almost like little punch marks) in regular parrern horizontally around the journal. Took photo but crap camera.
Could this be electrial discarge on the bearing journal? is so why no evidence in the bearings?